1. Field of the Invention
The present invention relates to an imaging apparatus, having focus detection pixels arranged on an imaging surface, for carrying out focus detection using phase difference AF, and being capable of correcting swirl error that arises in a subject having inclination with respect to a detection direction, and to an imaging method.
2. Description of the Related Art
Imaging surface phase difference AF, where focus detection pixels that have a phase difference detection capability are arranged on parts of an image sensor, and focus detection is carried out using phase difference AF, is known. It is also known, in a case of carrying out imaging in order to display a live view image, to perform readout at high speed by thinning out some pixels within the image sensor, in order to increase the readout speed (frame rate) (refer to FIG. 2, which will we described later).
When reading out a pixel signal from the image sensor by thinning, if thinning is carried out so that there is reduced readout of focus detection pixels in order to improve image quality of the live view image, there will be a reduction in precision of phase difference AF. In the imaging apparatus disclosed in Japanese patent publication 2010-181751 (hereafter referred to as “patent publication 1”), therefore, AF priority mode and image quality priority mode are provided, and readout is carried out in accordance with each mode.
Depending on arrangement of the focus detection pixels, precision of phase difference AF is lowered if there is inclination of a subject image with respect to the phase difference detection direction. This is because when different pixel rows of opening sections that have been provided on the focus detection pixels for detecting phase difference are arranged in a direction perpendicular to the phase difference detection direction, for a subject image that has contrast edge portions of the subject image inclined with respect to the phase difference detection direction, phase is offset by a rotation angle of contrast edge sections of the subject image, even in a focused state (refer to FIG. 2, which will be described later). In order to address this point, with the imaging apparatus disclosed in Japanese patent laid-open No. 2014-137505 (hereafter referred to as “patent publication 2”) it is proposed to correct phase offset due to rotation angle of the focus detection pixel arrangement.
In previously described patent publication 1, reduction in AF precision due to phase offset by a rotation angle that arises when focus detection pixels have been arranged is not resolved. Also, in patent publication 2 no consideration whatsoever has been given to the case where focus detection pixels have been reduced in number due to a thinned readout mode.